Photosynthetic Properties of Different Drought Resistant Chicory Strains and their Responses to Drought Stress

The photosynthetic properties and photosynthetic responses to drought stress in the pot experiment of three chicory (Cichorium intybus L.) strains with different drought resistance, space-mutagenesis-bred strains PA-82 and PA-43 and their initial strain PA-57 were studied using Li-6400 portable photosynthesis system. The results showed that diurnal time courses of net Photosynthetic rate (Pn), Transpiration rate (Tr), stomatal Conductance (Cond) presented as double-peak curves. There was an obvious midday Pn depression, which was caused by nonstomatal factors. Highest Pn, Tr and Cond values were observed in PA-82 and lowest corresponding values in. PA-43 (p<0.05). Intercellular CO2 Concentration (Ci) of three strains showed an opposite course to that of Pn which reached its valley at 10:00-1 2:00. PA-82 had the highest Water Use Efficiency (WUE), followed by PA-57, then PA-43. Light Saturation Points (LSP) of three strains were between 1207-1264 mu mol/m(2)/sec and Light Compensation Points (LCP) were between 14.55-14.85 mu mol/m(2)/sec, both indicating good adaptation to changes of light intensity. Pn, Tr, Cond, maximal photochemical efficiency of PS II in dark adaptation (Fv/Fm), potential photochemical efficiency (Fv/F0) and coefficient of Photochemical quenching (qP) decreased with the aggravation of water deficit. Among the three strains, the parameters of PA-43 dropped to a greater extent at a highest speed, followed by PA-57 then PA-82. With the aggravation of water deficit, Ci and co-efficient of nonphotochemical quenching (qN) increased to a greater extent at a highest speed in. PA-43. The results suggest that PA-82 and PA-57 have higher resistance against severe water deficit in comparison with PA-43.